This invention relates generally to a zone air-conditioning control or air conditioning system for the passenger compartment of a motor vehicle, and more particularly, the present invention relates to a zone air-conditioning control system which is capable of controlling the climate in air-conditioning zones covering each one of the passenger seats independently of each other.
Temperatures at various places in a passenger compartment of a motor vehicle are sometimes different from each other due to external influences such as sun light or the like. Furthermore, even if the temperature in the compartment is controlled to be uniform throughout various places in the compartment, the temperature at which a passenger feels comfortable is apt to be different for different passengers. Therefore, in some air-conditioning control systems known hitherto, air conditioning is effected in such a manner that its effect at each passenger's seat varies independently of the effect at other seats, or its effect is intentionally unbalanced.
According to the simplest example, air distribution is unbalanced by means of distribution valves provided in an air sending duct which leads temperature-conditioned air to a plurality of air discharging outlets provided at various places in the compartment. Although temperature difference is caused by the difference in airflow between various places in the compartment, a drastic unbalance in airflow is not preferable because the air conditioning felt by each passenger is subject to the changes in the airflow. For this reason it is difficult to provide a comfortable air-conditioning control, with which temperatures at all the places are kept uniform or a large temperature difference is provided, by only changing airflow. This also applies to other ways of providing airflow control, for example, by a plurality of electric fans each provided at each outlet for controlling airflow at each air outlet, or by providing a fin for the adjustment of the air blowing direction at each air outlet.
Apart from the control by airflow distribution change, it is also known that more than one temperature adjustment unit can be provided so that each covers a zone or region in the vehicle compartment. The best known example of this type is a so-called dual air-conditioning system having a main air-conditioning unit which controls the air around the front seat and a rear air-conditioning unit which controls the air around the rear seat, where these two units are respectively disposed at the front and rear of the compartment. Although this type of control is capable of controlling the temperature of each zone independently of the other zone, if the number of zones to be controlled is more than two, namely if each of the front and rear seats is divided into two zones of right seat and left seat, the above-mentioned control of airflow distribution change has to be used. Therefore, the control employing more than one temperature adjustment unit cannot provide satisfactory temperature adjustment.
According to another known example, a vehicle compartment is treated as a group of a plurality of air-conditioning zones, as disclosed in Japanese Patent Provisional Publication No. 56-2213, and at least one air outlet and a temperature adjustment unit are provided for each air-conditioning zone so that temperature control for each zone can be effected independently of other zones. It is known that the temperature of air blowing into each air-conditioning zone can be freely adjusted by controlling the corresponding temperature adjustment unit for the air-conditioning zone. However, in typical passenger motor vehicles, the passenger compartment has a space for four or more passengers. Therefore, at least four air-conditioning zones are needed, and thus at least four temperature adjustment units are needed. This makes the structure of the air-conditioning system complex and bulky. Furthermore, such a system requires a plurality of air ducts connected between the respective temperature adjustment units and the corresponding outlet or outlets, resulting an increase in the airflow resistance.